Association

Contents
1. Introduction 1
2. Theoretical background 5
2.1. The challenge of stabilizing stoichiometric europium oxide ........... 5
2.2. Electronic structure of EuO .............................. 8
2.2.1. The open shell 4f 7 .............................. 9
2.2.2. Valence band, band gap, and conduction bands .............. 10
2.3. Magnetic properties of EuO ............................. 11
2.3.1. The Curie temperature of EuO ........................ 14
2.3.2. Thin film effects in EuO ........................... 15
2.3.3. Spin filter tunneling in EuO ......................... 16
2.4. Hard X-ray photoemission spectroscopy ...................... 18
2.4.1. The three-step model of photoemission .................. 19
2.4.2. Spectral features and their interpretation ................. 23
2.4.3. Implications of hard X-ray excitation .................... 25
2.5. Magnetic circular dichroism in core-level photoemission ............. 29
2.5.1. Atomic multiplet theory including MCD .................. 29
2.5.2. Coupling schemes of angular momenta in Eu 2+ core-levels ....... 31
3. Experimental details 35
3.1. Molecular beam epitaxy for oxides ......................... 35
3.2. In situ characterization techniques ......................... 38
3.2.1. Reflection high-energy electron diffraction ................. 38
3.2.2. Low-energy electron diffraction ....................... 40
3.2.3. Auger electron spectroscopy ......................... 41
3.3. Experimental developments at the Oxide-MBE setup ............... 42
3.4. Ex situ characterization techniques ......................... 45
3.4.1. Superconducting quantum interference device magnetometry ..... 45
3.4.2. X-ray diffraction methods .......................... 46
3.4.3. Hard X-ray photoemission spectroscopy .................. 48
3.4.4. Depth-selective profiling with HAXPES .................. 51
3.4.5. Hard X-ray circular magnetic dichroism in photoemission ........ 55
vii